1. Field of the Invention
This invention relates to a process for utilizing the heat content of condensate and/or vapour produced in the manufacture of sugar.
2. Description of the Prior Art
As is known, in the processing of 1 ton of sugar beets, about 1 ton of condensate is obtained from the second and succeeding evaporators of the multiple effect evaporating plant for the concentration of the juice from the vacuum pans for boiling and crystallizing the juice and from the preheaters for preheating the juice. The condensate thus produced has merely been flash evaporated to the end point of the final evaporator of the evaporating plant (about 1 bar, 100.degree. C.) (see ULLMANNS Encyklopadie der technischen Chemie, 3rd Edition, Volume 19, page 239) and partially used for the heating of raw and preliming juice and of fresh extraction water. Nevertheless, even with optimum utilization of heat, to each ton of processed sugar beets, 0.4 to 0.6 ton of condensate at a temperature of 60.degree.-70.degree. C. leave the factory as unutilized effluent.
Depending upon the boiling scheme applied in a particular sugar factory, there are produced in the crystallization by the boiling plant, 250 to 300 kg of superheated vapour at a pressure of 0.2 to 0.25 bar and a temperature of 60.degree.-70.degree. C. per ton of processed beets, which must predominantly be condensed with cold water and thereafter introduced into the drainage system as so-called condenser water or cooled by means of a re-cooling circuit. To a small extent, vapour produced by boiling is also used for preheating raw and preliming juice, as well as fresh extraction water.
In all, in the procedure presently employed in a German sugar factory, about 800,000 kJ per ton of processed beets are lost as waste heat in condensates and vapour.
In addition, in Germany, the condensates and vapours produced in a sugar factory must now be cooled at considerable cost before they can be discharged as effluent because of anti-pollution laws.